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Subject: Re: contact stiffness, convergence, and solution time.
Author: Bill Bulat
Date: 2002-09-30 12:56:00

Hi Roberto,

The sparse solver may be used in a generation pass at release 6.1 (it's a
beta feature).

I tried it and it seemed to work with a very small test model. I don't see a
.tri file in my working directory however. Presently, I'm not certain you
could do an expansion pass (I believe you need the .tri file for that). You
CAN do a use pass, however. If you have 6.1 and don't need to do an
expansion pass, you might consider substructuring.

Bill Bulat
ANSYS Inc

----- Original Message -----
To:
Sent: Monday, September 30, 2002 11:28 AM

> I tryed to use substructuring tecnique, but I gave up because it is still
> using the frontal solver and has a limit on the number of elements used
> (46000), which made it much slower than solving the full model with sparse
> solver.
> The substructure method doesn't allow you to choose the solver.

> Regards,

> Roberto Porto
> DSC Engenharia

> ----- Original Message -----
> From: "Newland, Bill"
> To:
> Sent: Monday, September 30, 2002 11:48 AM
> Subject: RE: [xansys] RE: contact stiffness, convergence, and solution
time.

> > It's been a long time since I have done substructuring. Another
limitation
> > of the frontal solver which was also the only solver available for the
USE
> > pass was a limitation on the master degrees of freedom. I recall hitting
> > this limitation quickly with Contact52's in the USE pass interfacing
solid
> > model portions defined as superelements.

> > I was under the impression that Substructuring had become somewhat
> obsolete
> > with the advent of Solid92's and new solvers, but now that the Sparse
> solver
> > can be utilized for the Substructuring technique - maybe this technique
> > should be re-evaluated as a possible method to reduce run time for solid
> > model assemblies interfaced with Contact170/174's.

> > I was wondering if anyone has had any recent Substructuring experience
in
> > this regard.

> > Bill Newland
> > Bell Helicopter, Textron

> > -----Original Message-----
> > From: Metrisin Joe [mailto:jmetrisin@f...]
> > Sent: Friday, September 27, 2002 7:06 AM
> > To: 'xansys@yahoogroups.com'
> > Subject: [xansys] RE: contact stiffness, convergence, and solution time.

> > Several years ago, I wrote a macro that would automatically substructure
a
> > contact problem so that once the superelements were generated, you only
> had
> > to iterate on the contact elements. It wasn't very efficient because
you
> > had to use the frontal solver for the generation pass, which was about
20x
> > slower than solving the entire model once with the PCG solver.

> > The latest version of ANSYS now lets you do superelement generation with
> the
> > sparse solver, so it might be worth trying this technique again.

> > Joe Metrisin
> > Florida Turbine Technologies, Inc.

> > Date: Thu, 26 Sep 2002 13:20:17 -0500
> > From: "Newland, Bill"
> > Subject: contact stiffness, convergence, and solution time.

> > My compliments to Don Shaffer on expounding the need of faster solution
> > time for detailed models with contact elements!

> > Thanks to CAD transfers, automatic tetrahedron element meshing, and
> contact
> > elements - we are finally able to model interconnecting machine
components
> > as they really are. Now, if we could just do it without tying up our
> > computers for days.

> > One model I solved recently has about 800,000 dof's , 41 Contact 170/174
> > interface sets, and about 20,000 Contact 170/174 elements. I did get
good
> > results - but it took 6 cpu DAYS on an SGI Octane. Substantial modeling
> work

> > was expended to get the model size down without deleting important
detail.
> > While it is amazing that ANSYS can solve a problem like this at all, a
> much
> > faster turn around time is required in order to be practical.

> > Bill Newland
> > Bell Helicopter, Textron
Posts possibly associated with message #42306AuthorDateScore
42208contact stiffness, convergence, and solution time.Bill Newland2002/09/26 
42209Re: contact stiffness, convergence, and solution time.Dan Bohlen2002/09/26 
42210Re: contact stiffness, convergence, and solution time.Bill Kelly2002/09/26 
42228Re: contact stiffness, convergence, and solution time.Joe Metrisin2002/09/27 
42241Re: contact stiffness, convergence, and solution time.Bill Kelly bill.kelly@2002/09/27 
42303Re: contact stiffness, convergence, and solution time.Roberto Porto2002/09/30 
42306Re: contact stiffness, convergence, and solution time.Bill Bulat2002/09/30 
42307Re: contact stiffness, convergence, and solution time.Bill Bulat2002/09/30 
42315Re: contact stiffness, convergence, and solution time.Roberto Porto2002/09/30